Acid gas fractionation

ABSTRACT

A process to bulk separate H 2  S and CO 2  from a sour gas by first cooling the inlet sour gas, passing the cooled sour gas through a separator and removing a liquid acid gas as a bottoms product in a fractionation tower, and then either pumping or free flowing the liquid acid gas into a disposal well. Potential sulphur deposition problems are controlled by recycling liquid acid gas to the plant inlet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the separation of gases, and moreparticularly, to an improved method and system for the purification of asour gas stream by the bulk removal of CO₂ and H₂ S in a manner whichsubstantially lowers costs. The invention also provides a method forprevention of sulphur deposition in piping and equipment commonly foundin lean gas streams with high H₂ S and CO₂ concentrations.

2. Description of Related Art

Methods for bulk removal of H₂ S and CO₂ (acid gas) from a sour gasstream are well known, and include solvent-based Sour Gas Treating Units(SGTU), Ryan-Holmes, Rectisol, and other processes. The SGTU uses eitheran amine or physical solvent for removing the acid gas from the gasstream. The Ryan-Holmes process recirculates a lean oil additive toalter the solubility of the components in the system to prevent CO₂freezing problems in the fractionation column while removing H₂ S andCO₂. The Rectisol process uses a refrigerated methanol system forremoval of acid gas by physical absorption. See, for example, Holmes, A.S.; et al., "Process Improves Acid Gas Separation"; HydrocarbonProcessing, p. 131, May 1982; and "Advantages of Rectisol-Wash Processin Selective H₂ S Removal from Gas Mixtures", Line-Reports in Scienceand Technology, 18, 1973.

In 1962, Shell started up the Waterton Gas Plant near Pincher Creek,which had a "Low Temperature Flash" system. It liquified H₂ S at lowtemperatures, then flashed the H₂ S off at a lower pressure. This waseffective while the H₂ S concentration was high in the inlet gas stream.

Examples of such known methods and systems for the bulk removal of H₂ Sand CO₂ from a sour gas are disclosed in U.S. Pat. Nos., such as3,417,572 to Pryor, which discloses the separation of H₂ S from CO₂ bydistillation; 4,097,250 to Pagani et al., which discloses initialdesulfurization in a column by employing a solvent and then the removalof CO₂ by a low temperature distillation; 4,152,129 to Trentham et al.,which discloses the separation of CO₂ and methane in a gaseous mixture,with low energy consumption, if large amounts of CO₂ are present;4,293,322 to Ryan et al., which discloses the distillative separation ofCO₂ and H₂ S by adding a C₃ -C₆ akane to increase the relativevolatility facilities of the process; and 4,318,723 and 4,350,511 toHolmes et al., which disclose methods of distillative separation of CO₂and light hydrocarbons by adding a solids preventing agent and loweringthe temperature of the CO₂.

Most of the known methods recover acid gas containing H₂ S and CO₂ atlow pressures. This recovered acid gas then needs to be processedfurther in a Sulphur Recovery Unit (SRU), or compressed for injectioninto a disposal well. Since bulk acid gas removal is primarily apre-treatment process before a main processing facility, acid gascompression and injection into a disposal well is preferred for handlingthe waste acid gas stream. However, the high capital and operating costof removing and disposing of the acid gas using existing processes hasbeen a deterrent to the installation of bulk acid gas removalfacilities. Also, sulphur deposition is often a problem with lean sourgas compositions (mainly methane, H₂ S and CO₂, less than 1 mol. % andethane+), which can plug off piping equipment. When this occurs, theprocess must be shut down and cleaned either mechanically or by meltingthe sulphur deposits out.

Therefore, there exists a need in the art for an improved process forseparating H₂ S and CO₂ from a sour gas stream in a low cost manner, foruse in the field, or before a main processing facility, and for removingand preventing sulphur deposition without shutting down the process.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providean improved method for separating gases and handling sulphur depositionproblems. It is a particular object of the present invention to providean improved process for separating CO₂ and H₂ S from a sour gas stream.It is a further particular object of the present invention to provide animproved process wherein an inlet sour gas stream is cooled prior toentering a stripping column. It is a more particular object of thepresent invention to provide an improved process wherein an inlet sourgas stream is cooled prior to entering a stripping column where the bulkof hydrocarbons are stripped off and a liquid H₂ S and CO₂ stream isrecovered as a bottoms product. And, it is yet a still furtherparticular object of the present invention to provide an improvedprocess wherein an inlet sour gas is cooled, a liquid acid gas isstripped off from the sour gas in a column, and the liquid acid gas isthen either pumped or free-flowed down a disposal well.

In accordance with one aspect of the present invention, there isprovided an acid gas removal process for bulk removal of H₂ S and CO₂from a sour gas stream, which is simpler and greatly reduces the amountof acid gas compression required. An added benefit of the process is theremoval of trace sulphur compounds from the inlet sour gas streambecause this is a cold process. Trace sulphur compounds are removed withthe liquid H₂ S /CO₂ /CH₁ mixture in each separator and end up in theliquid acid gas stream. The process of the present invention works bycooling the inlet sour gas steam prior to entering a stripping columnwhere the bulk of the hydrocarbons are stripped off and a liquid H₂ Sand CO₂ stream is recovered as a bottoms product. The liquid acid gascan then be pumped or free-flowed down a disposal well. Part of theliquid acid gas steam is recycled to the inlet of the first gas/gasexchange for control or removal of sulphur deposits from equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention, which are believed tobe novel, are set forth with particularity in the appended claims. Thepresent invention, both as to its organization and manner of operation,together with further objects and advantages, may best be understood byreference to the following description, taken in connection with theaccompanying drawings, in which:

FIG. 1 is a schematic representation of a preferred embodiment of theprocess of the present invention;

FIG. 2 is a schematic representation of a second embodiment of theinvention; and

FIG. 3 is a schematic representation of a third embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description is provided to enable any person skilled inthe art to make and use the invention and sets forth the best modescontemplated by the inventor of carrying out his invention. Variousmodification, however, will remain readily apparent to those skilled inthe art, since the generic principles of the present invention have beendefined herein specifically to provide for an improved gas separationmethod.

Turning now to FIG. 1 of the drawings, there shown is a schematicrepresentation of a first embodiment of the process of the presentinvention. To prevent hydrate formation, water is first removed from aninlet sour gas stream 1 by molecular sieve dryers, or by injecting aninhibitor such as methanol therein. Dry, sour gas 1A is cooled by aGas/Gas Exchanger El and Chiller E2. This cooled sour gas 3 is fed intoa separator V1 and condensed liquid 3L composed mainly of methane, H₂ Sand CO₂ is separated therefrom and level controlled to a FractionationTower V3. Gas 3V from the top of V1 is further cooled in a Cold GasExchanger E3 before the pressure thereof is dropped across aJoule-Thompson valve VLV1 (a turbo-expander could also be used for powerrecovery). The pressure drop across the valve VLV1 reduces thetemperature to cryogenic levels. Downstream of the valve VLV1, a liquidacid gas 5L is separated from a cold gas stream 5 in Separator V2. Theliquid acid gas 5L, containing condensed methane and acid gases, is thenfed to the Fractionation Tower V3.

The Fractionation Tower is preferably a reboiled distillation columnwherein most of the methane and lighter hydrocarbons are distilled fromthe liquid feeds into the Fractionation Tower by hot stripping vaporsgenerated in the reboiler in a known manner. Enough heat is added to thereboiler to minimize the hydrocarbon content in the residual liquid acidgas bottoms product. The liquid acid gas bottoms product 14 recoveredfrom the distillation column V3 is at a high pressure and, therefore,can be pumped by P1, or free-flowed to a disposal well.

The overhead vapors 7 from the Fractionation Tower V3 are mixed with themain gas stream 8 from Separator V2 in a mixer M1. The mixed cold stream9 is warmed by passing through the shell side of exchangers E3 and E1.The warmed gas stream 11 is compressed to a required pressure bycompressor K-100. The compresser discharge gas stream 12 is cooled bycooler E4 before further processing.

If free sulphur is present in the sour gas stream 1 with a high H₂ Sconcentration, to prevent potential sulphur plugging problems of tubes,the liquid H₂ S /CO₂ 16 is recycled to the front end of the plant atMix-100. Sulphur is known to have a high solubility in liquid H₂ S(Smith J. J., Jensen, Dan and Meyer, Beat, "Liquid Hydrogen Sulfide incontact with Sulfur", Journal of Chemical and Engineering Data, Vol. 15,No. 1, 1970.), even at cold temperatures. By injecting liquid H₂ S intothe inlet gas stream at Mix-100, the equilibrium can be shifted toensure liquid H₂ S is formed in the first gas/gas exchanger El, as thegas stream 1A is cooled.

Sulphur deposition can also be controlled by allowing for solventinjection upstream of each exchanger. Some solvents which are effectivefor sulphur deposition problems include carbon disulfide (CS₂), dimethyldisulfide (DMDS), dialkyldisulfide mixtures (MEROX), anddiaryldisulfides (DADS).

The amount of recycled liquid will depend on the inlet sour gascomposition and the amount of sulphur (lbs. of sulphur/mmscf) present orexpected to form from pressure and/or temperature changes. Deposition ofsulphur can occur from a drop in temperature or pressure. Deposits canbe cleaned by either continuous recycling of liquid acid gas or batchrecycling of liquid acid gas.

The process can have other configurations than shown in FIG. 1. Forexample, as shown in FIG. 2, the acid gas fractionation system may haveinlet gas compression. This is necessary if the inlet gas pressure isless than about 800 psig. The inlet sour gas stream 1 is compressed in acompressor K-100, and the compressed gas 1A cooled by cooler E4 beforepassing through the first gas/gas exchanger E1 and chiller E2. Condensedliquids are then separated and fed to the Fractionation Tower V3, asdescribed above. That is, the gas stream is further cooled by a secondgas/gas exchanger E3 and by dropping the pressure across aJoule-Thompson valve VLV1. Condensed liquid is again separated from thecold stream and fed to the Fractionation Tower V3. Liquid acid gas isagain produced as a bottoms product from the Fractionation Tower V3. Theoverhead vapor stream 7 from V3 is combined with the main gas stream 8from separator V2 before being warmed in exchangers E3 and E1.

FIG. 3 shows a further embodiment, similar to FIG. 1, but aturbo-expander or similar power recovery device K2 is used in place ofthe Joule-Thompson valve VLV1 in the main process plant. This type of aset-up can reduce the horsepower required for sour gas compression by 20to 30%.

The amount of H₂ S and CO₂ recovered by the process of the presentinvention, can be varied by adjusting the pressure downstream of the JTvalve VLV1 or turbo expander K2, and by changing the Fractionation Towerbottoms temperature.

A lower pressure results in colder gas and more condensed liquid beforeseparator V2. Each of the above-mentioned processes needs to beevaluated for the practical lower limit on operating pressure andtemperature in a given installation. At some point, the amount ofmethane gas condensed from the gas stream will make further coolingimpractical.

Colder temperatures in the processes of the present invention can alsobe obtained by using other refrigerants (such as ethane or ethylene)instead of propane. However, caution must be exercised to ensure thatCO₂ freezing does not become a problem in the cold areas of the process.

It should be pointed out that the process design shown in FIG. 1 assumesshell and tube exchangers are used for the two gas/gas exchangers andthe chiller with temperature approaches of 10° F. Closer temperatureapproaches on exchangers can be obtained by using brazed aluminium heatexchangers. This can reduce chiller duty requirements resulting in asmaller refrigeration system.

The processes of the present invention are especially effective andeconomical if the sour gas stream to be treated contains highconcentrations of H₂ S and CO₂ and small quantities of ethane and higherhydrocarbons. The amount of H₂ S and CO₂ which can be removed depends onthe concentration of H₂ S and CO₂ in the sour gas stream. The process ismost economical for H₂ S and CO₂ concentrations of 10 mol % or greater.

This process on its own is economical for bulk removal of H₂ S and CO₂only. If sales gas and specifications for H₂ S and CO₂ have to be met,the processes of the present invention has to be augmented with adownstream SGTU.

The processes of the present invention save capital and operating costsby providing an efficient and simple system for bulk acid gas removal.The Acid Gas Fractionation Unit replaces the SGTU and acid gascompressors for bulk acid gas removal and can recover large quantitiesof liquid acid gas at high pressure. Liquid acid gas can now be pumpeddown a disposal well using a fraction of the horsepower required tocompress the same amount of acid gas from low pressures (which isrequired with other known systems for bulk acid gas removal).

Not only is the amount of acid gas compression reduced, but the totalinstalled horsepower for the acid gas fractionation facility (includingrefrigeration requirements) will be less than other systems. Forexample, a SGTU with acid gas compression would require in the order of15% or more installed horsepower than a comparable acid gasFractionation system of the present invention. As the processes of thepresent invention replace a large portion of the acid gas compressionwith much cheaper refrigeration compression, significant capital andoperating savings are realized. This is further illustrated in theexample presented below.

Case 1 is an example of the acid gas fractionation processes of thepresent invention for one possible inlet sour gas composition, asspecifically indicated therein. Many different inlet sour gascompositions are possible with varying H₂ S and CO₂ concentrations from10 mol. % to 85 mol. %.

Case 1 can be used to illustrate the advantages of the acid gasfractionation process over other bulk acid gas removal process, such asa Sour Gas Treating Unit, using a physical solvent.

Table 1 is a comparison of operating conditions and capital costs fortwo facilities designed for bulk acid gas removal from an inlet sour gasstream. The first facility uses the acid gas fractionation process ofthe present invention for removing the acid gas and recovering it in aliquid form for pumping down a disposal well. No acid gas compression isrequired with this design. The second facility uses a physical solventin a Sour Gas Treating Unit for removing acid gas.

The physical solvent is the best solvent choice for bulk acid gasremoval since it can be flash regenerated, eliminating the need for astripping column and reboiler. The process of a SGTU using a physicalsolvent instead of a chemical solvent has the advantage of recoveringsome of the acid gas at intermediate pressures by carrying out the flashregeneration in several steps using a high pressure separator, a mediumpressure separator and a low pressure separator. Acid gas from theseparators will flow to a multi-stage acid gas compressor before beinginjected into a disposal well.

The biggest difference between the two designs is the reduction ininstalled horsepower and the shift from sour compression to sweetcompression for the acid gas fractionation plant design using theprocess of the present invention. Less installed horsepower reducescapital costs and fuel gas consumption. Sweet compression is lessexpensive to install and costs less to maintain. These are the mainreasons for the lower capital cost of the facility of the presentinvention versus the SGTU plant design.

Equally important is the long term operating savings. With lessinstalled horsepower, more sweet compression and less sour compression,compressor maintenance costs will be reduced. There are also significantsavings in fuel gas of approximately $1.3 mm USD/yr (based on gas enginedrivers for compressor equipment and power generators, and a fuel gasvalue of $1.5/mscf, 1000 btu/scf) using the acid gas fractionationprocess. There are no solvent losses to replace as no solvent is used inthe process.

                  TABLE 1                                                         ______________________________________                                        COMPARISON OF PLANT OPERATION AND CAPITAL COSTS                               FOR A 100 MMSCFD BULK ACID GAS REMOVAL FACILITY                               WITH AN INLET COMPOSITION OF 20% H2S, 10% CO.sub.2,                           69% METHANE AND 1% ETHANE+                                                                  ACID GAS                                                        ITEM          FRACTIONATION                                                                              SGTU FACILITY                                      ______________________________________                                        Sour Compression                                                                            1500 hp      5100 hp                                            Sweet Compression                                                                           4500 hp      --                                                 Power Generation                                                                            700 hp       2600 hp                                            Total Operating HP                                                                          6700 hp      7800 hp                                            Fuel Gas Usage/Losses                                                                       1.5 mmscfd   3.9 mmscfd                                         Fuel Gas Costs @ $1.5                                                         per mmscf     $800,00 USD/yr                                                                             2,080,000 USD/yr                                   Solvent       None Required                                                                              Physical Solvent                                   used/circulation           2100 usgpm                                         Initial Fill                                                                  Chemical Costs                                                                              $50,000 USD  $2,000,000 USD                                     Installed Capital                                                             Cost (est.)   $23,500.00 USD                                                                             $26,170.00 USD                                     Estimated Yearly                                                              Operating Cost (Comp.                                                                       $2,300,000 USD                                                                             $3,800,000 USD*                                    Maintenance, Chemical                                                         Costs, Labor Costs,                                                           Fuel Gas Costs)                                                               ______________________________________                                         *Includes the cost of F.G. lost with the acid gas                        

    ______________________________________                                        ACID GAS FRACTIONATION                                                        CASE 1: 20% H2S, 10% CO2                                                      (AS INDICATED IN FIG. 1)                                                      E1                K1.DUTY                                                     DUTY -1.361e + 07 Btu/hr                                                                        POWER 1498. hp                                              E3                P1.DUTY                                                     DUTY -2.103e + 06 Btu/hr                                                                        POWER 190.6 hp                                              E2.DUTY           V3.REB.DUTY                                                 HEAT FLOW 1.379e + 07 Btu/hr                                                                    HEAT FLOW 6.485e + 06 Btu/hr                                E4.DUTY                                                                       HEAT FLOW 2.365e + 06 Btu/hr                                                  ______________________________________                                    

    __________________________________________________________________________    1 HYSYS Workbook Specsheet (All Pages) AG FRAC PLANT CASE 1.hsc               __________________________________________________________________________    4 Case (Main)                                                                 5                                                                             __________________________________________________________________________    7                                                                             8 Material Streams                                                            __________________________________________________________________________    9 Name            1     1a    2     3     3L                                  10                                                                            __________________________________________________________________________    11                                                                              Vapour Fraction 1.0000                                                                              1.0000                                                                              0.9747                                                                              0.7958                                                                              0.0000                              12                                                                              Temperature                                                                             (F.)  100.0*                                                                              100.0 11.50 -33.00*                                                                             -33.00                              13                                                                              Pressure  (psia)                                                                              1015.*                                                                              1015. 1005. 995.0 995.0                               14                                                                              Molar Flow                                                                              (MMSCFD)                                                                            100.0*                                                                              100.0 100.0 100.0 20.42                               15                                                                              Mass Flow (lb/hr)                                                                             2.483e+05                                                                           2.483e+05                                                                           2.483e+05                                                                           2.483e+05                                                                           6.972e+04                           16                                                                              Liquid Volume Flow                                                                      (USGPM)                                                                             1130. 1130. 1130. 1130. 213.8                               17                                                                              Heat Flow (Btu/hr)                                                                            -4.568e+08                                                                          -4.568e+08                                                                          -4.704e+08                                                                          -4.842e'08                                                                          -1.028e+08                          __________________________________________________________________________    18                                                                              Name      3V    4     5     5L    5V                                        19                                                                            __________________________________________________________________________    20                                                                              Vapour Fraction 1.0000                                                                              0.96729                                                                             0.9291                                                                              0.0000                                                                              1.0000                              21                                                                              Temperature                                                                             (F.)  -33.00                                                                              -42.10*                                                                             -55.86                                                                              -55.86                                                                              -55.86                              22                                                                              Pressure  (psia)                                                                              995.0 985.0 780.0*                                                                              780.0 780.0                               23                                                                              Molar Flow                                                                              (MMSCFD)                                                                            79.58 79.58 79.58 5.646 73.93                               24                                                                              Mass Flow (lb/hr)                                                                             1.785e+05                                                                           1.785e+05                                                                           1.785e+05                                                                           1.972e+4                                                                            1.588e+05                           25                                                                              Liquid Volume Flow                                                                      (USGPM)                                                                             916.5 916.5 916.5 59.26 857.2                               26                                                                              Heat Flow (Btu/hr)                                                                            -3.814e+08                                                                          -3.835+08                                                                           -3.835e+08                                                                          -3.160e+07                                                                          -3.519e+08                          __________________________________________________________________________    27                                                                              Name      6     7     8     9     10                                        28                                                                            __________________________________________________________________________    29                                                                              Vapour Fraction 0.1091                                                                              1.0000                                                                              0.9981                                                                              0.9964                                                                              1.0000                              30                                                                              Temperature                                                                             (F.)  -39.80                                                                              -45.97                                                                              -56.58                                                                              -56.21                                                                              -42.97                              31                                                                              Pressure  (psia)                                                                              780.0*                                                                              760.0 770.0*                                                                              760.0 750.0                               32                                                                              Molar Flow                                                                              (MMSCFD)                                                                            20.42 7.837 73.93 81.77 81.77                               33                                                                              Mass Flow (lb/hr)                                                                             6.972e+04                                                                           1.734e+04                                                                           1.588e+05                                                                           1.762e+05                                                                           1.762e+05                           34                                                                              Liquid Volume Flow                                                                      (USGPM)                                                                             213.8 90.83 857.2 948.0 948.0                               35                                                                              Heat Flow (Btu/hr)                                                                            -1.028e+08                                                                          -3.889e+07                                                                          -3.519e+08                                                                          -3.908e+08                                                                          -3.887e+08                          __________________________________________________________________________    36                                                                              Name      11    12    13    14    15                                        37                                                                            __________________________________________________________________________    38                                                                              Vapour Fraction 1.000 1.000 1.000 0.000 0.000                               39                                                                              Temperature                                                                             (F.)  90.00 145.0 120.0*                                                                              114.4 135.9                               40                                                                              Pressure  (psia)                                                                              740.0 1015.*                                                                              1010. 765.0 2000.*                              41                                                                              Molar Flow                                                                              (MMSCFD)                                                                            81.77 81.77 81.77 18.23 18.23                               42                                                                              Mass Flow (lb/hr)                                                                             1.762e+05                                                                           1.762e+05                                                                           1.762e+05                                                                           7.210e+04                                                                           7.210e+04                           43                                                                              Liquid Volume Flow                                                                      (USGPM)                                                                             948.0 948.0 948.0 182.2 182.2                               44                                                                              Heat Flow (Btu/hr)                                                                            -3.751e+08                                                                          -3.713e+08                                                                          -3.737e+08                                                                          -8.901e+07                                                                          -8.853e+07                          __________________________________________________________________________    45                                                                              Name      16    17                                                          46                                                                            __________________________________________________________________________    47                                                                              Vapour Fraction 0.000 0.000                                                 48                                                                              Temperature                                                                             (F.)  135.9 135.9                                                 49                                                                              Pressure  (psia)                                                                              2000. 2000.                                                 50                                                                              Molar Flow                                                                              (MMSCFD)                                                                            0.0000                                                                              18.23                                                 51                                                                              Mass Flow (lb/hr)                                                                             0.0000                                                                              7.210e+04                                             52                                                                              Liquid Volume Flow                                                                      (USGPM)                                                                             0.0000                                                                              182.2                                                 53                                                                              Heat Flow (Btu/hr)                                                                            0.0000                                                                              -8.853e+07                                            __________________________________________________________________________    54                                                                            55                                                                            56                                                                            57                                                                            58                                                                            59                                                                            60                                                                            61                                                                            62                                                                            63                                                                            64                                                                              Remarks:                                                                    65                                                                            __________________________________________________________________________

    __________________________________________________________________________    1 HYSYS Workbook Specsheet (All Pages) AG FRAC PLANT CASE 1.hsc               __________________________________________________________________________    4 Case (Main)                                                                 5                                                                             __________________________________________________________________________    7                                                                             8 Compositions                                                                __________________________________________________________________________    9 Name          1     2    10   11   3                                        10                                                                            __________________________________________________________________________    11                                                                              Comp Mole Frac (Nitrogen)                                                                   0.0050*                                                                             0.0050                                                                             0.0061                                                                             0.0061                                                                             0.0050                                   12                                                                              Comp Mole Frac (CO2)                                                                        0.1000*                                                                             0.1000                                                                             0.08014                                                                            0.08014                                                                            0.1000                                   13                                                                              Comp Mole Frac (H2S)                                                                        0.2000*                                                                             0.2000                                                                             0.06659                                                                            0.06659                                                                            0.2000                                   14                                                                              Comp Mole Frac (Methane)                                                                    0.6900*                                                                             0.6900                                                                             0.8436                                                                             0.8436                                                                             0.6900                                   15                                                                              Comp Mole Frac (Ethane                                                                      0.003000*                                                                           0.003000                                                                           0.002719                                                                           0.002719                                                                           0.00300                                  16                                                                              Comp Mole Frac (Propane)                                                                    0.001600*                                                                           0.001600                                                                           0.0008108                                                                          0.0008108                                                                          0.001600                                 17                                                                              Comp Mole Frac (CS2)                                                                        5.000e-05*                                                                          5.000e-05                                                                          6.365e-08                                                                          6.365e-08                                                                          5.000e-05                                18                                                                              Comp Mole Frac (COS)                                                                        0.0001000*                                                                          0.0001000                                                                          1.827e-05                                                                          1.827e-05                                                                          0.0001000                                19                                                                              Comp Mole Frac (M-Mercaptan)                                                                0.0002000*                                                                          0.0002000                                                                          2.284e-06                                                                          2.284e-06                                                                          0.0002000                                20                                                                              Comp Mole Frac (E-Mercaptan)                                                                5.000e-05*                                                                          5.000e-05                                                                          8.723e-08                                                                          8.723e-08                                                                          5.000e-05                                21                                                                              Comp Mole Frac (H2O)                                                                        0.0000*                                                                             0.0000                                                                             0.0000                                                                             0.0000                                                                             0.0000                                   __________________________________________________________________________    22                                                                              Name          3V    3L   12   13   4                                        23                                                                            __________________________________________________________________________    24                                                                              Comp Mole Frac (Nitrogen)                                                                   0.0061                                                                              0.0006                                                                             0.0061                                                                             0.0061                                                                             0.0061                                   25                                                                              Comp Mole Frac (CO2)                                                                        0.08626                                                                             0.1536                                                                             0.08014                                                                            0.08014                                                                            0.08626                                  26                                                                              Comp Mole Frac (H2S)                                                                        0.1016                                                                              0.5835                                                                             0.06659                                                                            0.06659                                                                            0.1016                                   27                                                                              Comp Mole Frac (Methane)                                                                    0.8021                                                                              0.2531                                                                             0.8436                                                                             0.8436                                                                             0.8021                                   28                                                                              Comp Mole Frac (Ethane                                                                      0.002798                                                                            0.003788                                                                           0.002719                                                                           0.002719                                                                           0.002798                                 29                                                                              Comp Mole Frac (Propane)                                                                    0.001051                                                                            0.003739                                                                           0.0008108                                                                          0.0008108                                                                          0.001051                                 30                                                                              Comp Mole Frac (CS2)                                                                        1.857e-06                                                                           0.0002376                                                                          6.365e-08                                                                          6.365e-08                                                                          1.857e-06                                31                                                                              Comp Mole Frac (COS)                                                                        3.768e-05                                                                           0.0003428                                                                          1.827e-05                                                                          1.827e-05                                                                          3.768e-05                                32                                                                              Comp Mole Frac (M-Mercaptan)                                                                2.016e-05                                                                           0.0009008                                                                          2.284e-06                                                                          2.284e-06                                                                          2.016e-05                                33                                                                              Comp Mole Frac (E-Mercaptan)                                                                2.175e-06                                                                           0.0002364                                                                          8.723e-08                                                                          8.723e-08                                                                          1.275e-06                                34                                                                              Comp Mole Frac (H2O)                                                                        0.0000                                                                              0.0000                                                                             0.0000                                                                             0.0000                                                                             0.0000                                   __________________________________________________________________________    35                                                                              Name          9     5    5V   5L   6                                        36                                                                            __________________________________________________________________________    37                                                                              Comp Mole Frac (Nitrogen)                                                                   0.0061                                                                              0.0061                                                                             0.0066                                                                             0.0005                                                                             0.0006                                   38                                                                              Comp Mole Frac (CO2)                                                                        0.08014                                                                             0.08626                                                                            0.07867                                                                            0.1857                                                                             0.1536                                   39                                                                              Comp Mole Frac (H2S)                                                                        0.06659                                                                             0.1016                                                                             0.06550                                                                            0.5742                                                                             0.5835                                   40                                                                              Comp Mole Frac (Methane)                                                                    0.8436                                                                              0.8021                                                                             0.8458                                                                             0.2303                                                                             0.2531                                   41                                                                              Comp Mole Frac (Ethane                                                                      0.002719                                                                            0.002798                                                                           0.002675                                                                           0.004404                                                                           0.003788                                 42                                                                              Comp Mole Frac (Propane)                                                                    0.0008108                                                                           0.001051                                                                           0.0007980                                                                          0.004364                                                                           0.003739                                 43                                                                              Comp Mole Frac (CS2)                                                                        6.365e-08                                                                           1.857e-06                                                                          6.254e-08                                                                          2.535e-05                                                                          0.0002376                                44                                                                              Comp Mole Frac (COS)                                                                        1.827e-05                                                                           3.768e-05                                                                          1.798e-05                                                                          0.0002958                                                                          0.0003428                                45                                                                              Comp Mole Frac (M-Mercaptan)                                                                2.284e-06                                                                           2.016e-05                                                                          2.245e-06                                                                          0.0002547                                                                          0.0009008                                46                                                                              Comp Mole Frac (E-Mercaptan)                                                                8.723e-08                                                                           2.175e-06                                                                          8.573e-08                                                                          2.954e-05                                                                          0.0002364                                47                                                                              Comp Mole Frac (H2O)                                                                        0.0000                                                                              0.0000                                                                             0.0000                                                                             0.0000                                                                             0.0000                                   __________________________________________________________________________    48                                                                              Name          7     14   15   8    1a                                       49                                                                            __________________________________________________________________________    50                                                                              Comp Mole Frac (Nitrogen)                                                                   0.0019                                                                              0.0000                                                                             0.0000                                                                             0.0066                                                                             0.0050                                   51                                                                              Comp Mole Frac (CO2)                                                                        0.09400                                                                             0.1891                                                                             0.1891                                                                             0.07867                                                                            0.1000                                   52                                                                              Comp Mole Frac (H2S)                                                                        0.07690                                                                             0.7984                                                                             0.7984                                                                             0.06550                                                                            0.2000                                   53                                                                              Comp Mole Frac (Methane)                                                                    0.8231                                                                              0.0009990                                                                          0.0009990                                                                          0.8458                                                                             0.6900                                   54                                                                              Comp Mole Frac (Ethane                                                                      0.003135                                                                            0.004259                                                                           0.004259                                                                           0.0032675                                                                          0.00300                                  55                                                                              Comp Mole Frac (Propane)                                                                    0.0009318                                                                           0.005140                                                                           0.005140                                                                           0.0007980                                                                          0.001600                                 56                                                                              Comp Mole Frac (CS2)                                                                        7.408e-08                                                                           0.0002740                                                                          0.002740                                                                           6.254e-08                                                                          5.000e-05                                57                                                                              Comp Mole Frac (COS)                                                                        2.100e-05                                                                           0.0004666                                                                          0.0004666                                                                          1.798e-05                                                                          0.0001000                                58                                                                              Comp Mole Frac (M-Mercaptan)                                                                2.651e-06                                                                           0.001087                                                                           0.001087                                                                           2.245e-06                                                                          0.0002000                                59                                                                              Comp Mole Frac (E-Mercaptan)                                                                1.014e-07                                                                           0.0002739                                                                          0.0002739                                                                          8.573e-08                                                                          5.000e-05                                60                                                                              Comp Mole Frac (H2O)                                                                        0.0000                                                                              0.0000                                                                             0.0000                                                                             0.0000                                                                             0.0000                                   __________________________________________________________________________    61                                                                            62                                                                            63                                                                            64                                                                              Remarks:                                                                    65                                                                            __________________________________________________________________________    1 HYSYS Workbook Specsheet (All Pages) AG FRAC PLANT CASE 1.hsc               __________________________________________________________________________    4 Case (Main)                                                                 5                                                                             __________________________________________________________________________    7                                                                             8 Compositions                                                                __________________________________________________________________________    10                                                                              Name          16    17                                                      __________________________________________________________________________    11                                                                              Comp Mole Frac (Nitrogen)                                                                   0.000 0.000                                                   12                                                                              Comp Mole Frac (CO2)                                                                        0.1891                                                                              0.1891                                                  13                                                                              Comp Mole Frac (H2S)                                                                        0.7984                                                                              0.7984                                                  14                                                                              Comp Mole Frac (Methane)                                                                    0.0009990                                                                           0.0009990                                               15                                                                              Comp Mole Frac (Ethane)                                                                     0.004259                                                                            0.004259                                                16                                                                              Comp Mole Frac (Propane)                                                                    0.005140                                                                            0.005140                                                17                                                                              Comp Mole Frac (CS2)                                                                        0.0002740                                                                           0.0002740                                               18                                                                              Comp Mole Frac (COS)                                                                        0.0004666                                                                           0.0004666                                               19                                                                              Comp Mole Frac (M-Mercaptan)                                                                0.001087                                                                            0.001087                                                20                                                                              Comp Mole Frac (E-Mercaptan)                                                                0.0002739                                                                           0.0002793                                               21                                                                              Comp Mole Frac (H2O)                                                                        0.0000                                                                              0.0000                                                  __________________________________________________________________________    22                                                                            23                                                                            24                                                                            25                                                                            26                                                                            27                                                                            28                                                                            29                                                                            30                                                                            31                                                                            32                                                                            33                                                     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                                    49                                                                            50                                                                            51                                                                            52                                                                            53                                                                            54                                                                            55                                                                            56                                                                            57                                                                            58                                                                            59                                                                            60                                                                            61                                                                            62                                                                            63                                                                            64                                                                              Remarks:                                                                    65                                                                            __________________________________________________________________________

Those skilled in the art will appreciate that various adaptations andmodifications of the just-described preferred embodiments may beconfigured without departing from the scope and spirit of the invention.Therefore, it is to be understood that, within the scope of the appendedclaims, the invention may be practiced other than as specificallydescribed herein.

What is claimed is:
 1. Process for the bulk removal of H₂ S and CO₂ froma sour gas stream, which comprises:a) feeding a dry, sour gas streamcontaining a mixture of H₂ S and CO₂ Into a gas/gas exchanger and achiller to cool the dry, sour gas; b) feeding the cooled, dry, sour gasinto a separator to obtain a gaseous top product and a condensed liquidacid gas bottoms product; c) feeding the condensed liquid acid gasbottoms product to a fractionation tower, to strip further vapors fromthe condensed liquid acid gas bottoms product and obtain a pressurized,condensed liquid acid gas bottoms product and over head vapors; and d)combining and mixing the gaseous top product from the separator and theoverhead vapors from the fractionation column and feeding them into thegas/gas exchanger to exchange heat with the dry, sour gas stream.
 2. Theprocess of claim 1 wherein said gaseous top product from said separatoris further cooled to a cryogenic level and fed to a further separatorwhere a further condensed liquid acid gas is obtained as a bottomsproducts, which further condensed liquid acid gas bottoms product fromsaid further separator is fed to said fractionation tower.
 3. Theprocess of claim 2 wherein said gaseous product from said separator isfurther cooled in a cold gas exchanger and the pressure thereof isdropped across a Joule-Thompson valve.
 4. The process of claim 2 whereinsaid gaseous product from said separator is further cooled in a cold gasexchanger and the pressure thereof is dropped across a turbo-expander.5. The process of claim 2 wherein said further condensed liquid acid gasbottoms product is at an elevated pressure, and may be pumped or freeflowed into a disposal well.
 6. The process of claim 5, furtherincluding a compressor to compress said dry, sour gas stream before saidgas/gas exchanger and said chiller so as to raise the pressure of saiddry, sour gas stream.
 7. The process of claim 6 wherein said gaseousproduct from said separator is further cooled in a gas exchanger and thepressure thereof is dropped across a turbo-expander.
 8. The process ofclaim 1, further including a mixer at said inlet to said gas/gasexchanger and said chiller, and mixing a portion of said pressurizedcondensed liquid acid gas bottoms product with said dry, sour gas streamto prevent or remove sulphur deposits.
 9. The process of claim 1,further including a compressor to compress said dry, sour gas streambefore said gas/gas exchanger and said chiller so as to raise thepressure of said dry, sour gas stream.
 10. The process of claim 9wherein said gaseous product from said separator is further cooled in agas exchanger and the pressure thereof is dropped across aturbo-expander.
 11. The process of claim 1, further including the stepof pumping the pressurized, condensed liquid acid into a disposal well.12. The process of claim 1, further including the step of free flowingthe pressurized, condensed liquid acid gas bottoms product into adisposal well.
 13. The process of claim 1 wherein the pressurized,condensed liquid acid gas bottoms product is at an elevated pressure,and may be pumped or free-flowed into a disposed well.
 14. The processof claim 1 wherein the dry, sour gas stream has a combined H₂ S and CO₂concentration greater than 10%.
 15. The process of claim 14 wherein thedry, sour gas stream has a combined H₂ S and CO₂ concentration from 10%to 85%.
 16. Process for the bulk removal of H₂ S and CO₂ from a sour gasstream which comprises:a) feeding a dry, sour gas stream containing amixture of H₂ S and CO₂ into an inlet to a gas/gas exchanger and achiller, to cool the dry, sour gas; b) feeding the cooled, dry, sour gasinto a separator to obtain a gaseous top product, and a condensed liquidacid gas bottoms product; c) feeding the condensed liquid acid gasbottoms product to a fractionation tower, to strip further vapors fromthe condensed liquid acid gas bottoms product and obtain a furthercondensed liquid acid gas bottoms product and overhead vapors; d)cooling said gaseous top product from said separator to a cryogeniclevel and feeding said cooled gaseous top product to a further separatorwhere further condensed liquid acid gas is obtained as a bottomsproducts and further overhead vapors are obtained; the further condensedliquid acid gas bottoms product from said further separator being fed tosaid fractionation tower; e) combining and mixing the further overheadvapors from the further separator and the overhead vapors from thefractionation column and feeding them into the gas/gas exchanger toexchange heat with the dry, sour gas stream; and f) dropping thepressure of said gaseous product from said separator across aJoule-Thompson valve.
 17. The process of claim 16, further including thestep of mixing a portion of said pressurized condensed liquid acid gasbottoms product with said dry, sour gas stream at the inlet to thegas/gas exchanger.
 18. The process of claim 16 wherein the dry, sour gasstream has a combined H₂ S and CO₂ concentration greater than 10%. 19.Process for the removal of H₂ S and CO₂ from a sour gas stream whichcomprises:a) feeding a dry, sour gas stream containing a mixture of H₂ Sand CO₂ into an inlet to a gas/gas exchanger and a chiller to cool thedry, sour gas; b) feeding the cooled, dry, sour gas into a firstseparator to obtain a first gaseous top product, and a first condensedliquid acid gas bottoms product; c) feeding the condensed liquid acidgas bottoms product to a fractionation tower, to strip further vaporsfrom the first condensed liquid acid gas bottoms product and obtain asecond pressurized condensed liquid acid gas bottoms product andoverhead vapors; d) cooling said first gaseous top product from saidfirst separator to a cryogenic level in a cold gas exchanger and feedingsaid cooled first gaseous top product to a second separator where asecond condensed liquid acid gas is obtained as a bottoms products, anda second gaseous top product; the second condensed liquid acid gasbottoms product from said second separator being fed to saidfractionation tower; e) combining and mixing the second gaseous productfrom the second separator and the overhead vapors from the fractionationcolumn and feeding them into the gas/gas exchanger to exchange heat withthe dry, sour gas stream; and f) dropping the pressure of said firstgaseous top product from said first separator across a turbo-expander.20. The process of claim 19 wherein the dry, sour gas stream has acombined H₂ S and CO₂ concentration from 10% to 85%.